Gaseous discharge device



Aug. 23, 1932. I DE FOREST 1,873,558

GASEOUS DISCHARGE DEVICE 4 Original Filed July 13, 1929 dttozmq PatentedAug. 23, 1932 UNITED STATES PATENT OFFICE LEE DE FOREST, 0] HOLLYWOOD,CALIFORNIA, ASSIGNOR '10 GENERAL TALKING PIC- TUBES CORPORATION, OF NEWYORK, N. Y., A CORPORATION OF DELAWARE GASEOUS DISCHARGE DEVICE Originalapplication filed July 13, 1929, Serial No. 877,987. Divided and thisapplication flled'December 1, 1980. Serial No. 489,885.

This invention relates in general to gas filled electron dischargedevices particularly designed for photographic recording of fluctuatingcurrents and especially for photographic sound recording.

The present a plication is a division of my application file July 13th,1929, Serial No. 377,937.

One of the objects of this invention is the provision of a gaseousdischarge device which has a longer life as compared with devices ofthis type now known.

Another object of this invention involves the construction of anelectron discharge device which is not subject to blackening of theglass walls of the enclosing envelope.

A still further object of this invention is the provision of a device ofthis type so constructed that after operation for a few hours itsoperation becomes stable and the amount of light given off under anyexcitation is practically constant.

An additional object of this invention is to provide an electrondischarge device of such construction that the cathode absorbs the gasescontained within the envelope and the materials therein to a less degreethan is now commonly experienced.

A still further object of the invention is to employ a cathode indevices of this of molybdenum.

These and other objects as will appear from the following disclosure aresecured by means of the device of this invention.

This invention resides substantially in the combination, construction,arrangement, and relative location of parts, all as will be described ingreater detail hereinafter.

Referring to the drawing:

Figure 1 is a longitudinal cross-sectional view through one form ofdevice embodying the principles of this invention.

Figure 2 is an end elevational view of the device; and

Figure 3 is a sectional view of a modified form of device.

Heretofore any gaseous discharge devices as known when employed forsound recordin purposes and the like have a short useful 11ft, usuallyof only a few hours duration.

This short life is due chiefly to blackening of passes due to thedeposition on theinterior of the glass containing vessel of metallicparticles torn off by the discharge from the surface of the electrodesor electrode. It is also due in part tothe gradual absorption of gasesby the electrodes or by the insulating material in the tube. Thisinvention has to do with the construction of gaseous discharge deviceswhich avoids the aforementioned difiiculties and furnishes a dischargetube which has an indefinite life, the light from which after a fewhours use, attains a definite stable value and remains practicallyconstant.

Some of the advantages of a device of this nature, which is known in theart as a phot1on, are derived from the fact that a cathode made ofmolybdenum is employed. Other features which produce the advantages ofthis invention lie in the fact that the cathode is surrounded by anenvelope of insulating material and is so constructed that it may beplaced very close to the rounded, smooth end or window of the glassvessel. In addition, the end of the cathode is polished so that it actsas a mirror, thereby somewhat increasing the illuminating efficiency ofthe discharge device. By employing molybdenum as the cathode metal andby shaping it so that the outer surface thereof is flat and set oppositeand close to the window end of the tube it has been found that the glassdoes not become blackened as the molybdenum does not lose any of itsparticles that otherwise would be shot off from the surface of thecathode and to a great extent deposited upon the glass. This particularfeature in the glow tube for photographically recording sound, is ofgreat importance, as the glass end or window of the tube must be kept asclear and transparent as possible. It is therefore desirable that ametal be used, not to absorb gas, but to prevent blackening of the glassend or window of the tube.

Referring to the drawing, the elements of the discharge tube areenclosed within a glass envelope 1 which is sealed off in the usualmanner at 2 after being evacuated and filled, as is well known in theart, with a suitable gas,or mixture of gases. The vessel or envelope 1has a reentrant stem 3 protube 3 and formed integrally therewith is avhollow tube 8 lying parallel to the central axis of the envelope.Extending through this tube is a lead-in-wire 11 which connects to ashort length of platinum wire 10 sealed in the end thereof. Separated bythe platinum wire 10 and encircling the insulating sleeve 6 at a shortdistance from the end thereof is the anode or second electrode 9- in theform of a ring. The lead wire 12 passes through the press 4. and isconnected to the cathode 7 of the device. With a gas of suitablepressure within the envelope and a proper current excitation impressedacross the leads 11 and 12 a luminous gas discharge is formed betweenthe cathode and the anode up close to the end wall of the vessel 1. Asis well known in this art, the end of the vessel is rounded in form andmade as smooth and clear as possible so that accurate transmission ofthe light is secured therethrough. The end of the cathode 7 for bestperformance is polished to give a mirror-like surface.

In the modified form of device shown in Fig. 3 the anode 14 consists ofa single view curved around and terminating short of the end surface ofthe cathode 7. The discharge then occurs between curved anode wire 14and the cathode 7 It is important that the cylinder, of insulatingmaterial 6 in both cases fit tightly over the glass tube 5 so that anelectrical discharge can never take place from the lead-in wires withinthe insulating cylinder 6. As is clear from the drawing the anode ring 9is very close to the exterior surface of the insulating sleeve but isactually out of contact therewith. In actual construction the cathode iswithin one-eighth to three-sixteenths of an inch of the interior of theglass envelope and the anode ring approximately one-quarter of an inchfrom the forward end of the insulating sleeve 6. If desired largelead-in wires can be employed, particularly the wire 12, so as toproperly conduct away the heat from the discharge which is generated atthe cathode surface. The lead-in wires, where they pass through theseals, will of course conform to any standard practice whereby anairtight connection is secured.

It has been found that tantalum and molybden um are the best materialsfor the oathode. When tantalum is used there is no observable depositionupon or blackening of the glass envelope even after man hours of thelike are employed; Platinum can be advantageously employed as cathodematerial but the expense involved would be unneces sarily great.

From the foregoing disclosure it will be apparent that I have devised anew and novel construction in electron discharge devices which employcertain'principles of construction and operation which may assume otherphysical forms than those disclosed in the drawing for purposes ofillustration. do not, therefore, desire to be strictly limited to thedisclosure as given for purposes of illustration but rather tothe scopeof the appended claims. I

What I seek to secure by United States Letters Patent is:

1. A glow tube for photographically recording sound, including atransparent glass envelope and a molybdenum cathode mounted in theenvelope and having a flat surface disposed opposite and close to thelight emitting end of the envelope. Y I

2. A glow tube for photographically recording sound as claimed in claim1, wherein the flat surface of the cathode is highly polished.

3. A glow tube as claimedin claim 1, wherein the cathode is a doublediametered cylindrical member, the larger base end of which is flattenedand polished.

In testimony whereof I affix my signature.

' LEE DE FOREST.-

